How your BMR is calculated

This tool uses the Mifflin-St Jeor equation, which research has found to be the most accurate of the common BMR formulas for the general population. It uses weight, height, age and sex:

For men: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5. For women: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161. The result is the energy, in calories per day, needed just to keep your body running — breathing, circulating blood, and maintaining temperature — if you did nothing else all day.

From BMR to daily calories (TDEE)

BMR is only the baseline. Your Total Daily Energy Expenditure (TDEE) adds the calories you burn through movement and digestion. The table above multiplies your BMR by a standard activity factor — from 1.2 for a sedentary lifestyle up to 1.9 for hard daily training — to estimate how much you actually burn.

To lose weight, most guidance suggests eating a few hundred calories below your TDEE; to gain, a modest surplus. A deficit of roughly 500 calories a day is a common, sustainable target for gradual fat loss, but very low intakes are best supervised by a professional.

What affects your metabolism

Muscle is more metabolically active than fat, so people with more lean mass tend to have higher BMRs — one reason strength training helps with long-term weight management. BMR also naturally declines with age and is influenced by genetics, hormones and body size. These estimates are population averages and individuals can vary by 10% or more, so use the number as a planning guide rather than an exact prescription.

Frequently asked questions

Sources & references

1. Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. "A new predictive equation for resting energy expenditure in healthy individuals." Am J Clin Nutr. 1990;51(2):241–247.